In the year 950 Lotario, King of Italy, dies young, leaving a widow, Adelaide, daughter of Rodolfo di Borgogna (Rudolph of Burgundy). Berengario, into whose hands the government of the kingdom had already fallen some time before, manages to get himself elected successor. However, he is suspected of having caused his predecessor’s sudden death, and so he tries to neutralize the claims of Adelaide and her supporters, ordering her to marry his own son Adelberto, who reigns with him. Adelaide refuses and, persecuted, is forced to run away and wander from one wild spot to another in an attempt to hide herself. She finally finds refuge with Iroldo in the fortress of Canossa and, when the castle is besieged by Berengario, she summons help from the Emperor Ottone (Otho), promising him her hand in marriage and the rights to the crown of the Kingdom of Italy that she has inherited.

Act One

The first scene is set inside the fortress of Canossa, which has been taken by storm by Berengario. Whilst the victors exult and the people bewail the fortunes of their country and of the princess Adelaide, Adelberto, supported by his father, tries to persuade her to become his bride, although she is still dressed in mourning for her deceased husband. Hearing that Ottone is in the neighbourhood, Berengario, knowing that he does not have enough troops to challenge him on the battlefield, decides to deceive him with false overtures of peace. In the second scene the action moves to the Emperor’s camp. The soldiers, busily erecting tents, sing a hymn to Italy, whilst Ottone solemnly swears that Lotario’s widow shall be saved. Adelberto, sent by Berengario, offers Ottone peace and hospitality, advising him not to trust Adelaide, whom he describes as an ambitious woman who loves stirring up trouble. The third scene takes place in the great hall of the fortress, where Berengario, putting on a pretence of cordiality, welcomes Ottone, who at once asks to meet Adelaide. She herself now appears before the Emperor, imploring him to have pity on her and help her obtain justice for her wrongs. Ottone promises her his help and, attracted to the princess, declares that he wishes to make her his bride. The two depart, leaving Adelberto, who is deeply in love with Adelaide, and would like to get rid of Ottone at once, but Berengario restrains him, urging him to wait for the arrival of their own troops before striking. In the fourth scene Adelaide, no longer dressed in mourning, is in her rooms with her attendant ladies: she wishes to be sad no longer and she is cheered by the thought of her approaching marriage. Ottone comes in, wanting to be reassured that she has accepted him as her husband for love and not for mere gratitude; Adelaide convinces him of the sincerity of her love and the two swear eternal fidelity. The last scene shows the main square of Canossa surrounded by imposing buildings. Ottone and Adelaide set off for the wedding ceremony in the church, accompanied by the festive songs of the crowd. Berengario and Adelberto are bursting with impatience and finally, when their troops arrive, they show their true intentions by attacking Ottone and his soldiers. All of a sudden we have passed from a holiday atmosphere to fighting and confusion. Adelaide is led away by Berengario’s warriors, whilst Ottone and his men, fighting hard, manage not to be overcome by the enemy.

Act Two

The first scene returns us to the interior of the fortress, where Berengario’s warriors are exulting at having put Ottone to flight. Adelberto once more offers Adelaide the opportunity of sharing the throne with him, but, as before, she greets his words with disdain. Their conversation is interrupted by the news that the fortunes of war have overturned the apparent victory: Ottone has conquered Berengario and made him prisoner. In the second scene Eurice begs her son Adelberto to exchange Adelaide for Berengario, as proposed by a messenger sent by the Emperor. Torn between his love for the princess and his filial duty, Adelberto cannot decide; and so Eurice, in order to avoid Berengario’s being condemned to death, hits on the plan of secretly helping Adelaide to escape with the help of Iroldo. The third scene is set in the Imperial encampment, where Ernesto, an officer of Ottone’s, announces the arrival of Adelberto. The latter is disposed to give up Adelaide, but Berengario proudly opposes this: he will only restore the princess to her friends if he is guaranteed the throne. Ottone agrees to this; however, the unexpected arrival of Adelaide, set free by Eurice, nullifies the agreement and persuades the Emperor to hold Berengario prisoner still, with a view to having his revenge upon him. Now Adelaide, who had promised Eurice that in exchange for her freedom she would guarantee that Eurice’s husband would be released, demands that Ottone respect her promise. Berengario and Adelberto are thus allowed to leave the camp, but they withdraw swearing that they will come back fully armed to score a definitive victory. In the following scene, the interior of a magnificent tent, Adelaide reluctantly says farewell to Ottone, who is about to face the final decisive battle, giving him her veil as a pledge of her love; she then implores heaven’s help and, whilst she is engrossed in her prayers, the news arrives that the enemy has been defeated. The final scene shows the return of Ottone and his army to the fortress of Canossa: the Emperor is drawn in on a triumphal car followed by Adelberto and Berengario in chains, while the people, rejoicing, throw flowers and laurel wreaths.